Over the years various types of illuminating assemblies and devices have been developed for indoor and/or outdoor illumination, such as incandescent bulbs, fluorescent bulbs, halogen lights, and light emitting diodes. Incandescent light bulbs create light by conducting electricity through a thin filament, such as a tungsten filament, to heat the filament to a very high temperature so that it glows and produces visible light. Incandescent light bulbs emit a yellow or white color. They are very inefficient, as a high percentage of energy input is lost as heat. Fluorescent tube lamps conduct electricity through mercury vapor, which produces ultraviolet (UV) light. The ultraviolet light is then absorbed by a phosphor coating inside the lamp, causing it to glow, or fluoresce. The most common formats are ¼ inch diameter (T2), ⅝ inch diameter (T5) and 1 inch diameter (T8) and with length ranging from about 6 inches to 8 feet. The 4 foot long, 1 inch diameter (T8) fluorescent lamp is one of the most widely deployed lamps worldwide in commercial and industrial settings.
While the heat generated by fluorescent lamps is much less than their incandescent counterparts, energy is still lost in generating the UV light and converting UV light into visible light. If the lamp breaks, exposure to mercury can occur. Linear fluorescent lamps are often five to six times the cost of incandescent bulbs but have life spans around 10,000 and 20,000 hours. Some fluorescent lights flicker and the quality of the fluorescent light tends to be a harsh white due to the lack of a broad band of frequencies. Most fluorescent lights are not compatible with dimmers.
A typical fluorescent overhead lighting assembly provides overhead ceiling lighting with a ceiling fixture comprising an outer housing containing an electronic ballast, starter and wiring, and metal concave reflectors positioned above one or more fluorescent tube lamps to reflect emitted light downwardly toward the floor. The ballast associated with the lighting fixture converts AC line voltage to the DC power provided to the fluorescent tube. The ballast also reduces the power supply to a voltage level suitable for use in a florescent tube. A starter circuit for providing a voltage pulse is needed to cause current to conduct through the ionized gas in the fluorescent tube. One type of fixture is adapted to be integrated into a drop ceiling support grid, and may include a transparent or translucent lens incorporated as a tile of a grid pattern drop ceiling for diffusing and/or focusing emitted light. Another fixture type is configured to be mounted to the main structural ceiling. Low bay fixtures suspend from a ceiling using chains or cabling.
Conventional fluorescent lighting fixtures also include mounting brackets for securing light sockets for holding and electrically connecting the fluorescent lamps. The fluorescent tube lamps typically utilize a bi-pin/2-pin means on the tubular body that mechanically supports the body in an operative state on the light sockets or lamp holders of the ceiling lighting fixture and effects electrical connection of the illumination source to a power supply. The bi-pins are inserted into slots in the lamp holders and then rotated to secure the connection.
Light emitting diode (LED) lighting is particularly useful. Light emitting diodes offer any advantages over incandescent and fluorescent light sources, including: lower energy consumption, longer lifetime, improved robustness, smaller size, faster switching, and excellent durability and reliability. LEDs emit more light per watt than incandescent light bulbs. LEDs can be tiny and easily placed on printed circuit boards. The printed circuit board may comprise, for example, a conventional printed circuit board, a specialized printed circuit board (e.g., a flexible printed circuit board), single-sided, double-sided, multilayer or any other appropriate type of wiring board, all of which are generically referred to herein as a “printed circuit board” or “PCB” herein. LEDs activate and turn on very quickly and can be readily dimmed. LEDs emit a cool light with very little infrared light. They come in multiple colors which are produced without the need for filters. LEDs of different colors can be mixed to produce white light. The operational life of some white LED lamps is 100,000 hours, which is much longer than the average life of an incandescent bulb or fluorescent lamp. Another important advantage of LED lighting is reduced power consumption. An LED circuit will approach 80% efficiency, which means 80% of the electrical energy is converted to light energy; the remaining 20% is lost as heat energy. Incandescent bulbs, however, operate at about 20% efficiency with 80% of the electrical energy lost as heat. LED-based solid-state lighting (SSL) is now a mainstream technology, replacing incandescent, halogen, and compact fluorescent lights in commercial, industrial, and residential use. It is to be noted that “light emitting diode” and “LED” in the context of the present invention also means organic light emitting diodes.
Linear LED tube lamps are available for directly replacing fluorescent lamps in an existing light fixture. The most common lamp formats approximate the overall appearance and dimensions of their fluorescent counterparts. LED tube lamps typically comprise an array of LEDs mounted on one or more circuit boards. The LED boards are mounted on an elongate heat sink comprising a heat conducting material such as aluminum. The LED circuit boards are in thermal contact with the heat sink, but are electrically isolated from the heat sink. The LED tube lamp may include internal driver circuitry for converting AC line current to DC current and reducing and controlling the voltage applied to the LEDs. The internal driver circuitry can be designed specifically to meet the electrical requirements of the LED circuit boards, thus overcoming potential problems associated with using the existing local ballast originally designed for powering fluorescent lamps. In some designs, however, an external local ballast is used. The high power LEDs, as well as any internal driver, generate heat that must be dissipated by the heat sink. To facilitate heat dissipation to the atmosphere, the heat sink is typically disposed such that its external surface forms a portion of the outer surface of the tube lighting assembly. The lighting assembly is installed with the heat sink facing upward toward the ceiling lighting fixture. The remaining circumference of the tube comprises a translucent or transparent lens cover through which the generated light is emitted towards the space to be illuminated.
The most common type of LED tube lamp is designed to be retrofit into the insert and rotate type lamp holders mounted on conventional fluorescent ceiling lighting fixtures, known in the industry as “tombstone” lamp holders. Such lamp holders are connected to AC line voltage. They were originally developed to engage the pair of electrical power pins projecting in cantilever fashion from the end caps of a cylindrical shaped fluorescent tube lamp. LED tube lamps mimicking this bi-pin end cap arrangement are now available for direct retrofit into the tombstone lamp holders. Although widely deployed for decades throughout the industry, this connector format has certain disadvantages. The exposed pins on the ends of the linear tube lamp are susceptible to damage during distribution and installation. The lamp body must be situated in a first angular orientation to direct the pins into the lamp holders mounted on a support/reflector and is thereafter turned to effect mechanical securement and electrical connection. Installation requires a precise initial angular orientation of the body and subsequent controlled repositioning thereof to simultaneously seat the pins at the opposite ends of the body. Often one or more of the pins are misaligned during this process so that electrical connection is not established. The same misalignment may cause a compromised mechanical connection whereupon the body may escape from the connectors and drop so that it is damaged or destroyed.
Further, the tombstone lamp holders on the support/reflector are generally mounted in such a fashion that they are prone to flexing. Even a slight flexing of the holders on the support might be adequate to release the pins at one body end so that the entire body becomes separated. The conventional bi-pin and tombstone lamp holder connector means was created for very lightweight fluorescent lighting and not designed for the additional weight of LED tubular lighting due to the required heat sink and PCB boards. The weight of the body by itself may produce horizontal force components that wedge the connectors on the support/reflector away from each other so that the body becomes precariously situated or fully releases.
Another problem with this type of lighting configuration, particularly with an LED illumination source, is that the connectors at the ends of the lamp body are by their nature difficult to consistently assemble. Typically, the manufacturing process will involve steps of soldering conductive components on the end connectors and illumination source. Wires are commonly used in these designs, with the ends thereof soldered during the assembly process. If the conductive components are not properly connected, the system may be inoperable. Soldered connections are also prone to failing when subjected to forces in use. Generally, it is difficult to maintain a high level of quality control, regardless of the care taken in assembling these types of components. Aside from the quality issue, the assembly steps that involve the electrical connection of the conductors are inherently time consuming and may require relatively skilled labor, and/or expensive automated systems. Disassembly of such lamps presents similar difficulties and expense. As a result of these difficulties associated with assembly and disassembly, refurbishing such lamps to replace defective or worn out components is difficult to justify economically. In most cases, the entire lamp assembly will simply be discarded and replaced with a new lamp assembly, and as a result, lamp components that have significant useful life remaining are wasted.
Another approach for replacing fluorescent tube lighting with LED lighting involves replacing fluorescent lighting fixtures with integrated LED fixtures. Integrated LED linear lighting fixtures provide a completely new fixture rather than replacement lamps for existing fixtures. In other words, the LED light engines and other electrical components are permanently mounted within an outer fixture housing to create an integrated overall unit, as opposed to fixtures equipped with lamp mounting sockets for permitting separate LED lamps to be installed in and removed from the fixture housing. One example uses LED strips fixedly mounted across the face of a thin rectangular troffer housing, which can in turn be mounted into a standard ceiling infastructure. Such fixtures are typically more expensive than replacement LED tubes, and they entail the additional time, labor and cost of removing and disposing of the existing fluorescent lighting fixtures and altering the current fixture design and possibly also the layout. This reduces the potential return of the investment to upgrade to more efficient LED technology, increases the time and complexity of designing and installing LED lighting for a given facility, and increases the likelihood of scheduling conflicts and disruptions of the work environment of the facility. Integrated LED fixtures also prevent the user from making performance upgrades with simple lamp replacement as lamp technology improves, or from addressing non-functioning LEDs or other components by simply replacing a defective individual lamp.
While first generation LED lighting products for the fluorescent tube replacement market were designed to be powered by AC line voltage, which is converted to lower DC voltage via an external ballast or internal driver circuit as explained above, there are efforts underway to power LED lighting by using power over Ethernet (PoE) technology. PoE provides both data and power connectivity in one cable so that powered devices do not require a separate cable for each need. PoE has been used, for example, to power IP telephones, IP cameras, wireless access points, and remote Ethernet switches. PoE can provide DC power over long cable runs, e.g. hundreds of feet. Universal Serial Bus (USB) and IEEE 1394 (FireWire) are examples of other standardized technologies for high-speed data transfer, both of which also provide data and power, albeit over more limited distances compared to PoE. These are commonly used for connecting peripherals to personal computers and recharging digital devices such as smartphones. These standards may regulate communication, encoding and device addressing protocols, port specifications, cabling requirements, connector designs, etc. to assure compatibility among devices, components and products, and to provide plug-and-play capability. For the purpose of providing context for the inventions disclosed herein, the following discussion relates principally to communicating power and data according to Ethernet standards. However, as will become apparent, the inventions disclosed below are by no means limited to PoE implementations and are also applicable to other standardized technologies capable of using a single cable to provide both data connectivity and electrical power to devices.
Systems communicating over Ethernet networks divide a stream of data into shorter pieces called frames, with each frame containing source and destination addresses. Each Ethernet station is given an address. The addresses are used to specify both the destination and the source of each data packet. In a modern Ethernet, each station communicates with a switch, which in turn forwards that traffic to the destination station.
In a typical PoE implementation, 120V electrical wiring (240V in Europe) terminates at power sourcing equipment (PSE), typically one or more Ethernet switches used to plug in computers, phones, printers, and other devices to a local area networks (LAN). In addition to communicating data, the PSE transmits DC power over standard Ethernet cabling to the powered devices. Available Ethernet switches can supply up to 60 W of power per port, and this power capability is expected to increase with additional technology and standards development in this area.
There are several known techniques for transmitting power over Ethernet cabling. The most common forms used are 10BASE-T, 100BASE-TX, and 1000BASE-T. All three utilize twisted pair cables. Fiber optic variants of Ethernet have also been proposed, and may offer certain performance advantages. Standards-based PoE implemented using twisted-pair cables for the physical layer of the network follow the specifications of IEEE 802.3. The standard Ethernet cables have four pairs of twisted wires. Category 5 cable, commonly referred to as “Cat5,” is currently widely used. Most Cat5 cables are unshielded, relying on the balanced line twisted pair design and differential signaling for noise reduction. Each of the four pairs in a Cat5 cable has differing precise number of twists per meter to minimize crosstalk between the pairs. Category 5 was superseded by the category 5e (enhanced) specification, and later category 6 cable, which supports Gigabit Ethernet. Category 7, the newest cable standard for Ethernet and other interconnect technologies, features four individually shielded pairs as well as an overall cable shield to protect the signals from crosstalk and EMI. This allows supporting higher frequency signals and carrying more data than Cat5 and Cat6 cable.
Standard modular connectors are used to connect the devices of an Ethernet LAN. Male plugs serve to terminate loose cables and cords, and female jacks are incorporated into fixed locations on surfaces such as walls and panels, and on equipment. These modular connectors latch together via a spring-loaded tab on the plug, which snaps into the jack so that the plug cannot be easily pulled out. To remove the plug, the latching tab may be depressed.
Modular connectors come in 4-, 6-, 8-, and 10-position sizes, where a position is a location for a contact or pin. The contacts, commonly referred to as insulation displacement contacts or “IDCs,” have sharp prongs that, when crimped, pierce the insulation and connect with the wire conductor. Not all of the positions may have contacts installed, or, alternatively, some contacts may not be connected to a wire conductor. The insulating plastic bodies of 4-position and 6-position connectors have different widths, whereas 8-position or 10-position connectors share an even larger body width. A very common connector is known as an RJ45 connector, which is a modular 8 position, 8 pin connector used for terminating Cat5 or Cat6 twisted pair cable in Ethernet over twisted pair networks.
The 10BASE-T data transmission standard, and its successors, 100BASE-TX and 1000BASE-T, support speeds of 10, 100 and 1000 Mbit/sec respectively. Only two of the four pairs are needed for 10BASE-T or 100BASE-TX. Power may thus be transmitted on the unused conductors of a cable, which is referred to as Alternative B. Power may also be transmitted on the data conductors using a phantom power technique of applying a common-mode voltage to each pair. In the IEEE standards, this is referred to as Alternative A. It may be used with 10BASE-T and 100BASE-TX, as well as with 1000BASE-T, which uses all four pairs for data transmission. This is possible because all versions of Ethernet over twisted pair cable specify differential data transmission over each pair with transformer coupling. The DC supply and load connections can be made to the transformer center-taps at each end. Each pair thus operates in common mode as one side of the DC supply, so two pairs are required to complete the circuit.
The IEEE PoE standards provide for signaling between the PSE and powered device. This signaling allows the presence of a device to be detected by the power source, and allows the device and source to negotiate the amount of power required or available. The PSE decides whether power mode A or B shall be used. A powered device indicates that it is standards-compliant by placing a standardized resistor between the powered pairs. If the PSE detects a resistance that is too high or too low (including a short circuit), no power is applied. The original IEEE PoE standard provides up to 15.4 W of DC power to each device. The updated standard, also known as PoE plus, provides up to 25.5 W of power.
LED lighting offers intriguing possibilities for PoE implementation due to low power requirements and compatibility with digital connectivity and control. Investigators have proposed that PoE LED lighting can eliminate the cost, regulations and infrastructure associated with AC line voltage, which delivers power far beyond what LED lights need. Ethernet cable can safely carry the much lower DC voltages required, without the need and associated cost of using certified electricians for installation and maintenance. PoE enabled LED lighting also eliminates the electronics to convert main-line AC to DC, and the power loss associated with converting AC to DC current at each lamp. Installation is also safer because of the relatively low DC voltage involved.
Because LED lighting is based on diodes combined with other solid state circuits, it is adaptable to serve as network nodes to receive, collect and transmit information using sensors, wireless communications modules and processors embedded in LED lighting fixtures. For example, each LED hub can collect information on ambient light conditions, temperature, humidity, room-occupancy data, etc., which it then communicates back to a controller. Occupancy sensing can ensure that lighting turns on when someone enters a room and turns off when the room is unoccupied. Ambient light sensors can adjust the lighting to maintain constant lighting throughout the day. Other componentry can collect LED lamp usage data and power draws to support maintenance and warranty issues, and can identify opportunities for improved energy usage and operational efficiency. PoE is well-suited for powering, connecting, and controlling smart LED lighting hubs with a local area network (LAN) in this manner.
Networked LED lighting is poised to play a major role in the Internet of Things (IoT), using Ethernet local area networks to power and control smart hubs containing LED light engines, sensors and communication modules. Historically when businesses wish to reconfigure existing space, electricians are brought back to modify the lighting branch circuits and fixture position. This is costly and time consuming. In larger buildings, lighting systems are powered by a separate and dedicated 120/277V AC infrastructure. If controls are needed (such as for vacancy sensing or daylight harvesting) a second communication network is often added. This overlay infrastructure is usually a standalone network. Both the 120/277V AC infrastructure and control communication network add huge costs to the building owner in the form of high capital expense, design engineering “soft costs” and added maintenance complexity. In short, existing AC lighting systems are costly to install, maintain and operate. And once installed, they are inflexible. In contrast, PoE LED lights enables customers to safely move lights, adjust color temperature and automate failure detection—all while getting a better experience and saving energy. Operational data can be generated or collected by smart LED lighting hubs (e.g., light conditions, usage data, occupancy and link to Building Automation Systems, BAS) and communicated back to central control unit for enabling a wide range of automation control strategies.
Although PoE enabled LED lighting systems offer potential advantages, development efforts to date have focused primarily on increasing the power available from the PSE and reducing the power requirements of LED light engines. While these developments have improved the efficiency comparison between a PoE LED system and more conventional AC system, they have essentially bypassed the conventional tube lamp format that is widely deployed throughout the world. PoE LED systems heretofore proposed bring integrated power and data to specially designed integrated LED light fixtures, which are designed to replace entire fluorescent light fixtures. These present offerings require removing and replacing each fluorescent lighting fixture with a PoE enabled integrated LED fixture, which is very costly and erodes the value proposition of transitioning to LED lighting. There are presently no means available to directly connect individual LED tube lamps designed to retrofit conventional fluorescent lamps to an Ethernet LAN to become individually addressed and managed nodes of a networked lighting system. As explained above, known LED linear tube lamps are designed to be powered using AC line voltage, which is converted to lower voltage DC current by the ballast of the legacy fluorescent lamp fixture or using driver circuitry internal to the lamp itself. The external bi-pin conductors of conventional linear lamps not only provide an electrical path for inputting external power to the lamp, they also mechanically secure each lamp end in the corresponding tombstone lamp holder of the fixture. It is not possible to run data and power through the bi-pin conductors.
An alternative “snap-fit” type connector system adapted for a modified form of a linear LED tube lamp is shown in U.S. Patent Application Publication 2014/0293595, by the same applicant of the subject application, and which is incorporated as if reproduced in its entirety herein. The tubular LED lighting assembly disclosed therein has at least one LED emitter board within the body; and first and second connectors respectively at the first and second body ends that are configured to secure the lamp on a support fixture. The first connector has cooperating first and second parts. The first connector part is integrated into an end cap assembly of the lamp body. The second connector part is configured to be on a support for the tubular lighting assembly. The first and second connector parts respectively have first and second surfaces. As the second connector part is received within an opening of the end cap assembly, the first and second surfaces are placed in confronting relationship to prevent separation of the first and second connector parts as an incident of the first connector part moving relative to the second connector part from a position fully separated from the second connector part in a substantially straight path that is transverse to the length of the lamp body.
This “snap-fit” connection does not utilize exposed pins to mechanically secure the lamp ends to the support. The connection is effected by a linear motion rather than an insert and rotate technique. The first end cap assembly may include at least a first connector board. The connector board comprises generally L-shaped pins housed within the end cap assembly, each having a first portion extending in a direction generally parallel to the length of the body and a second portion extending in a direction traverse to the length of the body and towards the second connector part when said first connector part is moved towards the second connector part and into the engaged position. The conductive components on each of the first and second connector parts electrically connect to each other to form an electrical path between the illumination source and an external AC power supply as an incident of the connector parts being moved into the snap-fit engaged configuration. This previously proposed snap-fit connector system addresses some of the problems associated with the use of conventional tombstone type lamp holders for securing LED tube lamps to lighting fixtures. However, it too is configured for only traditional means of powering LED light engines from AC line power, and is not adapted to communicate both power and data using Ethernet or any other integrated power and data distribution standard.
Accordingly, known implementations of PoE LED overhead lighting for replacing fluorescent tube lighting are architected around integrated LED fixtures as the powered devices. In such systems, each integrated LED fixture is provided with a standard Ethernet jack, typically a RJ-45 jack for accepting an RJ-45 Ethernet cable plug. The LED fixture as a unit thus becomes a plug-and-play device with its own address. Power and data communication are provided to the fixture as a unit, which distributes the power internally to individual LEDs and other components using internal circuitry. As previously explained, such integrated LED fixtures utilize LED strips rather than conventional tube lamp form factors, and eliminate the numerous advantages of the LED tube form factor. In particular, installing an integrated PoE enabled LED fixture entails significant expense compared to simply replacing individual fluorescent tubes with replacement LED tubes. The expense of removing and disposing of existing fluorescent lighting fixtures and altering the current fixture design and layout may substantially offset the cost savings associated with these promising means of powering LED lighting. Integrated LED fixtures also constrain the property owner to the technology available at installation, making it more difficult and expensive to upgrade as communication, sensor, control and other technologies improve.
LED lighting systems built as an assemblage of integrated LED fixtures suffer from these and other disadvantages not only in conventional lighting applications, such as commercial buildings and schools, but also in more specialized contexts such as horticultural lighting systems. These systems are used in greenhouses or other environments where living organisms are irradiated with light to support plant growth. Indoor commercial plant farms are now producing fruits, vegetables and grains within urban areas, reducing transportation costs and carbon footprint in addition to minimizing land usage. Whether in a greenhouse setting requiring supplemental light or an indoor setting relying completely on artificial light, LED lighting has the potential to significantly reduce the electrical cost for greenhouse operators and indoor farmers. Furthermore, research into how specific spectral bands are primarily responsible for different stages of the horticultural growth cycle has made LEDs an even more attractive lighting option. It is believed that a broad-spectrum source, such as a sodium lamps, essentially wastes energy producing radiation in portions of the spectral band such as green, which has been shown thus far to have minimal to no benefit to plant growth.
It has been shown that LEDs can significantly stimulate plant growth while reducing energy consumption. The light engines typically deployed in LED horticultural systems are integrated LED fixtures and lack the lamp form factor. One known manufacturer has marketed an LED tube lamp for replacing powered fluorescent tube lamps in an AC powered horticultural lighting systems. The lighting systems for which the lamp is intended do not deploy PoE technology. The applicant is not presently aware of any horticultural lighting system designed to be powered and controlled using the capabilities of PoE or any other standardized power and data technology.
There is a need for LED lighting that provides the benefits of PoE technology in the linear tube format that is widely deployed throughout the lighting industry. As used herein, the terms “LED tube lamp” and “linear LED lamp” and similar variants are used interchangeably to describe LED lamps having at least one LED board mounted on an externally exposed heat sink having a narrow and elongated overall profile and with optional elongated optical lens, and designed for removable mounting to a variety of lighting fixture housings. While the overall form factor of such lamps is ordinarily generally similar to that of conventional fluorescent tube lamps, the use of these terms is not intended to limit the scope of the disclosed or claimed subject matter to lamps having any particular lateral cross-sectional shape or to require a fully enclosed outer tubular structure. As will be apparent from the disclosure herein, these terms are also intended to encompass variants of such lamps designed to be removably mounted directly to a ceiling grid or other support structure. These terms, however, are to be distinguished from integrated LED lighting fixtures in which LED boards and heat sink components are mounted to an outer fixture housing in the absence of a removable modular LED light engine lamp component. While PoE enabled LED fixtures are appropriate for certain installations, systems that enable individual LED tube lamps to directly connect as managed nodes of an Ethernet LAN would allow for numerous possibilities for the next phase of power and controls for commercial and residential lighting. The present invention is directed to safe, reliable, convenient and cost-effective solutions that will allow the benefits of PoE LED lamp technology to be fully realized in the LED tube format, greatly expanding the potential benefits of, and applications for, PoE enabled LED lighting.
Still another problem in the lighting industry are the difficulties and costs associated with proper design and control of emergency lighting circuits. Emergency lighting systems are required by a myriad of municipal, state, federal or other codes and standards. These systems are intended to automatically supply illumination to designated areas and equipment in the event of failure of the normal power supply, to protect people and allow safe egress from a building, and to provide lighting to areas that would aid rescuers or repair crews. These systems are typically required by regulation to be available within a short time (e.g. 10 seconds) after failure of normal power, and emergency circuits must be physically separated from all other circuits all the way to the terminations and the source. Other standby systems, although not legally required, may be desirable to provide lighting to prevent discomfort or serious damages to a product or process.
The proper design and control of emergency lighting circuits in compliance with the many standards and codes that may apply to a given site installation has long presented difficult challenges for manufacturers, systems integrators and electricians and engineers. As a result, a number of approaches to designing emergency or standby lighting circuits have been attempted. One known approach involves providing a number of emergency-only luminaires dedicated to providing minimum illumination levels and powered by a dedicated emergency breaker panel fed from a generator or uninterruptable power supply (UPS). An uninterruptible power supply is an electrical apparatus that provides emergency power to a load when the input power source, typically mains power, fails. A UPS differs from an auxiliary or emergency power system or standby generator in that it will provide near-instantaneous protection from input power interruptions, by supplying energy stored in batteries or a flywheel. Regardless of the source of back-up power, the emergency fixtures remain dark when normal power is present, and are energized when the control circuit detects failure of the normal power supply. This approach entails the potentially high cost of the emergency system equipment and may be visually unappealing as result of excess luminaries which are not illuminated during normal conditions.
Another approach involves self-contained battery pack emergency lights, which contain a battery, a charger, and a load control relay. These units are connected to normal power, which provides a constant charging current for the battery. During a power failure, the load control relay energizes the emergency lights. This approach avoids the need to deploy physically separated emergency circuits, but is typically implemented in aesthetically unpleasing forms resembling a car headlight battery pack unit. Still another approach uses the same light fixture for both normal an emergency use. The lights are fed using the normal breaker panel and wall mounted switch during normal operation. When power fails, an emergency transfer circuit transfers the breaker panel feed to an emergency power source, and bypasses the wall switch to force the load on the lights regardless of the wall switch position. Although such systems offer aesthetic advantages, they are expensive and complex to design and install. Other known approaches suffer similar drawbacks.
It is therefore desirable to provide improved LED lamps and associated connector systems which overcome some, if not all of the proceeding problems and disadvantages.